Multi-sectioned pulsed detonation coating apparatus and method of using same

Abstract

A pulsed detonation gun, according to one embodiment, has a first section into which a detonable mixture is injected and a second section into which a coating precursor is injected. A detonable or reactive mixture is formed and ignited in the first section, and the detonation or reaction products expand through the first section and into the second section into contact with the coating precursor. Detonation products containing the coating precursor are discharged through an outlet and contacted with a substrate to produce a coating. The device is particularly useful for coating the inside surfaces of small-diameter tubes and a variety of other difficult-to-reach substrate surfaces.

Description

FIELD OF THE INVENTION [0001] The present invention is directed to coating technology and, more particularly, to pulsed detonation coating (sometimes also referred to as pulsed thermal spray (PTS)). DESCRIPTION OF RELATED ART [0002] Several techniques have been used to implement thermal spray coating. One approach has been High Velocity Oxygen / Fuel System (HVOF), in which solid particles are injected in high velocity gas produced by reaction of oxidizer and a fuel at high pressure. Such systems typically are used for deposition at atmospheric pressure and primarily are used for coating metal alloys and cermets powders with particle sizes larger than about 10 μm. Other thermal spray coating techniques include plasma spray, in which particles are heated and accelerated by high temperature plasma produced by an electric discharge in an inert gas atmosphere. Plasma spray systems have been used for both atmospheric- and low-pressure coatings. [0003] Thermal spray coating also has been im...

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Benefits of technology

[0009] In another embodiment, an object is coated at a reduced standoff between the outlet of a pulsed detonation coating apparatus and the coated surface. Conventional detonation coating generally uses a standoff of 8 to 25 cm. In this embodiment, the standoff can be about 5 cm or less and usually ranges from about 2 mm to about 4 cm, and often ranges from about 3 mm to 3 cm, about 4 mm to 2 cm, or about 5 mm to 1 cm. Such reduced standoffs facilitate coating the inside of tubes, especially at corners, and assures uniform material distribution. The apparatus makes coating at these short standoffs possible because of its small size and because of the small particle sizes that can be used in the coating systems.

[0014] The detonation products produced by the pulsed detonation gun accelerate and heat the coating precursor or coating material particles to high kinetic energies, resulting in high quality coating depositions that can provide such properties as corrosion-, erosion-, and wear resistance. Existing thermal spray coating equipment is unsuitable for applying such coatings to the inner surfaces of small-diameter tubes and many other difficult-to-reach surfaces.

Problems solved by technology

However, coating particles never reach the velocity of detonation products due to inertia.

In current coating devices, the ranges of detonation temperature and pressure are intrinsically limited by the properties of the detonable mixture compositions and concentrations.

On the other hand, it is sometimes desirable to process materials at temperatures and pressures that are significantly lower than those typical for detonation waves and detonation products.

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